Substrate cleaning method and substrate cleaning apparatus

ABSTRACT

A substrate cleaning apparatus is provided that includes a cleaning cup for receiving a to-be-cleaned substrate, a table in the cleaning cup, a first, second, and third nozzles, a pure water heating mechanism configured to supply hot pure water, a branch line, a control mechanism, and an open/close valve, provided between the branch line and the pipe, wherein the open/close valve is configured to interrupt emission of hot water from the third nozzle by opening the open/close valve to lower the pressure in the pipe.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2000-190696, filed Jun. 26,2000, the entire contents of which are incorporated herein by reference.This application is a divisional of U.S. Ser. No. 09/887,141, filed Jun.25, 2001, now U.S. Pat. No. 6,632,289.

BACKGROUND OF THE INVENTION

This invention relates to a substrate cleaning method and substratecleaning apparatus for performing a cleaning process including a dryingprocess by use of liquid agents and pure water.

A semiconductor device such as an IC and LSI is formed by performing adesign step of designing an integrated circuit to be formed on asemiconductor substrate, a mask forming step of drawing a mask patternused for forming the integrated circuit by use of an electron beam, awafer forming step of forming a wafer with a preset thickness from asemiconductor single crystal ingot of silicon, for example, a waferprocessing step of forming semiconductor elements of the integratedcircuits and the like on the wafer, an assembling step of dividing thewafer into semiconductor chips and respectively packaging them to formsemiconductor devices, and a test step.

The wafer processing step includes a plurality of steps and a cleaningstep is further added thereto to remove dust such as organic-seriesimpurities attached while the steps are effected. Since the dustattached to the surface of the wafer may cause the manufacturedsemiconductor device to become defective, much effort has been made inorder to eliminate the dust. The cause for making the formedsemiconductor device defective by the dust attached to the surface ofthe wafer will not occur only in the case of the semiconductor device.For example, the same cause occurs in a case wherein a liquid crystaldisplay device is formed or a photo-mask used for forming thesemiconductor device or liquid crystal display device is formed, andtherefore, much effort has been made to eliminate dust in the processfor manufacturing the liquid crystal display device or the photo-mask.

Conventionally, in the manufacturing process of the semiconductordevice, the semiconductor substrate of silicon or the like is cleanedand polished by use of not only deionized water (pure water) andultra-pure water but also electrolyzed water obtained by electrolyzingthe pure water or ultra-pure water. So far, a fluorine-series solventhas been used for cleaning the semiconductor substrate and the like, butsince the solvent gives a bad influence on the living environments, itbecomes out of favor and water such as pure water and ultra-pure wateris utilized as the most safe solvent.

The pure water is water with high purity from which impurities such asions, fine particles, micro-organism and organic material are almostcompletely removed and whose resistivity is approximately 5 to 18 MΩcm.The ultra-pure water is water which has extremely high purity higherthan the pure water and from which suspension (suspended substances) anddissolved substances are removed with high efficiency by use of aultra-pure water forming device.

Conventionally, the cleaning process for the wafer or the like iseffected as follows. The wafer is rotated with the rear surface of thewafer held by a vacuum suction type spin chuck. Then, a cleaning liquidsuch as pure water is dropped from a nozzle onto a rotating roll-likebrush and the wafer surface is cleaned by bringing the brush intocontact with the wafer.

Conventionally, an acid liquid agent was continuously emitted onto ato-be-cleaned substrate in order to eliminate the organic-seriesimpurity, then the acid liquid agent on the to-be-cleaned substrate waswashed out by use of pure water and the to-be-cleaned substrate wasdried. The liquid agent was washed out before drying by spinning thesubstrate at a high speed, but the temperature of the pure water used atthis time was set at a room temperature. Further, when the to-be-cleanedsubstrate was spin-dried, the number of setting values of the rotatingspeed was only one. If a heating mechanism for the pure water or liquidagent was provided, the pressure in the pipe between the heatingmechanism and the emission port (nozzle) of the cleaning chamber was nottaken into consideration.

Thus, the conventional organic-series impurity removing process by useof the acid liquid agent exhibited an extremely high cleaning effect,but there was a possibility that the acid liquid agent adhered to theto-be-cleaned substrate. Further, the cleaning process by use of theacid liquid agent utilized the high reactivity thereof, and in thiscase, there occurred a possibility that splash of the liquid agentoccurred to contaminate the inner wall of the cleaning chamber (cup) andthe contaminant would fall on the to-be-cleaned substrate at the time ofdrying by high speed rotation.

Further, if the liquid agent is washed out by use of pure water of theroom temperature, the pure water remains at the center of the surface ofthe to-be-cleaned substrate to the last when the drying processutilizing centrifugal force caused by the high speed rotation iseffected. If the pure water of the room temperature runs on theto-be-cleaned substrate at high speed, static electricity occurs due tofriction between the pure water and the substrate surface, and thereoccurs a possibility that a pattern formed on the to-be-cleanedsubstrate is destroyed when charges are discharged.

If the cleaning liquid is set at a high temperature, the viscosity ofthe cleaning liquid becomes low, and friction between the inner wall ofthe pipe and the cleaning liquid becomes small. Leakage of the cleaningliquid from the nozzle will occur for a while after interruption ofemission of the liquid agent or the like due to a reduction in thefriction between the inner wall of the pipe and the cleaning liquid.Particularly, if pure water is kept leaked for a while when thesubstrate is spin-dried after washing-out by pure water, the leaked purewater will drop on the to-be-cleaned substrate.

This invention has been made to solve the above problem and an object ofthis invention is to provide a substrate cleaning method for efficientlyremoving an acid liquid agent remaining on a to-be-cleaned substrateafter cleaning in the method for cleaning the to-be-cleaned substrate byuse of an acid liquid agent and a substrate cleaning apparatus used inthe above substrate cleaning method.

BRIEF SUMMARY OF THE INVENTION

In order to attain the above object, a substrate cleaning methodaccording to a first aspect of this invention comprises cleaning ato-be-cleaned substrate disposed in a cleaning cup by use of an acidliquid agent; and cleaning the substrate by use of an alkaline liquidagent in the cleaning cup to neutralize residue of the acid liquid agentafter the step of cleaning by use of the acid liquid agent.

A substrate cleaning method according to a second aspect of thisinvention comprises oxidizing impurities on the surface of ato-be-cleaned substrate by use of an oxidizing agent; and cleaning theto-be-cleaned substrate by use of a reducing agent to remove theoxidized impurities after the oxidizing step.

A substrate cleaning apparatus according to a third aspect of thisinvention comprises a cleaning cup configured to receive a to-be-cleanedsubstrate; a table disposed in the cleaning cup, configured to supportthe to-be-cleaned substrate; a first nozzle disposed in the cleaningcup, configured to supply an acid liquid agent; a second nozzle disposedin the cleaning cup, configured to supply an alkaline liquid agent; athird nozzle disposed in the cleaning cup, configured to supply hot purewater; a pure water heating mechanism configured to supply the hot purewater; a branch line formed in an intermediate portion of a pipeextending from the pure water heating mechanism to the third nozzleconfigured to supply the hot pure water to lower water pressure in thepipe; and a control mechanism configured to control the operations ofthe first to the third nozzle and the pure water heating mechanism.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a schematic plan view of a substrate cleaning apparatus ofthis invention;

FIG. 2 is a flow chart for illustrating the process of a substratecleaning method of this invention;

FIGS. 3 and 4 are partial cross sectional views of a cleaning cup, forillustrating a cleaning method by use of acid liquid agent according toa second embodiment of this invention;

FIG. 5 is a partial cross sectional view of a cleaning cup, forillustrating a cleaning method of a cleaning cup according to a thirdembodiment of this invention;

FIG. 6 is a partial cross sectional view of a cleaning cup, forillustrating a substrate rinsing method according to a fourth embodimentof this invention;

FIG. 7 is a partial cross sectional view of a cleaning cup, forillustrating a substrate drying method according to a fifth embodimentof this invention; and

FIG. 8 is a schematic piping diagram for illustrating a branch lineaccording to a sixth embodiment of this invention.

DETAILED DESCRIPTION OF THE INVENTION

The feature of the cleaning method of this invention will be describedat first.

According to this invention, after the acid liquid agent is washed outby use of deionized water (pure water), an alkaline liquid agent isemitted to cause a neutralization reaction between the acid and alkaliso as to efficiently remove the acid liquid agent remaining on thesurface of the to-be-cleaned substrate. Further, in the substratecleaning method, the substrate temperature at the drying time can beraised by emitting hot pure water to the surface of the to-be-cleanedsubstrate before the spin drying process. At this time, the temperatureof the surface of the to-be-cleaned substrate can be made maximum at aportion near the center thereof by emitting hot pure water to a portionslightly separated from the center of the surface of the to-be-cleanedsubstrate.

As a result, the drying process can be started from the center of thesubstrate surface. Further, since the temperature of the to-be-cleanedsubstrate is raised, the surface of the to-be-cleaned substrate can bedried even if it is rotated at a speed which is not so high, and as aresult, the pure water will not run on the surface of the to-be-cleanedsubstrate at a high speed, thereby making it possible to reduce thefriction between the pure water and the substrate surface andsuppressing occurrence of static electricity. Even if the to-be-cleanedsubstrate is rotated at a high speed after the surface of theto-be-cleaned substrate is dried to a certain area, pure water will notrun on the substrate surface at a high speed.

Further, if the heating mechanism for pure water or liquid agent isprovided, a branch line is provided in an intermediate portion of thepipe between the heating mechanism and the emission port of the cleaningchamber and a valve is provided in the branch system so as to adequatelychange pressure in the pipe by opening or closing the valve.Particularly, if hot pure water is emitted before the spin dryingprocess, the pressure in the pipe can be lowered by opening the valve ofthe branch system at the same time as interruption of emission andliquid leakage from the nozzle can be prevented at the time of spindrying.

As the to-be-cleaned substrate to be treated in this invention, forexample, a wafer of silicon used as a material of a semiconductordevice, a liquid crystal substrate used as a material of a liquidcrystal display device, and a photo-mask used when the semiconductordevice and liquid crystal are formed can be exemplified.

There will now be described embodiments of this invention with referenceto the accompanying drawings.

(First Embodiment)

In the first embodiment, the basic construction of a substrate cleaningapparatus of this invention and the basic process of a substratecleaning method are explained. FIG. 1 is a plan view showing theschematic construction of the substrate cleaning apparatus of thisinvention and FIG. 2 is a flow chart for illustrating the substratecleaning process.

As shown in FIG. 1, the substrate cleaning apparatus 1 has loading andunloading cassettes 9 and 10 arranged therein and a cleaning cup 6 usedas a cleaning chamber. A rotating table 3 is disposed inside thecleaning cup 6. The rotating table 3 is supported by a rotating shaft 7arranged in the cleaning chamber and supports a to-be-cleaned substrate2. The rotating shaft 7 rotates the rotating table 3 supporting theto-be-cleaned substrate 2 at a high or low speed. The rotating table 3is constructed to partly support the substrate 2 (have an openingportion) so as to permit the rear surface of the to-be-cleaned subject 2to be cleaned.

In the cleaning chamber 6, an acid liquid agent supply nozzle 4 and purewater/alkaline liquid agent supply nozzle 5 are arranged with theemission ports thereof directed towards the front surface of theto-be-cleaned substrate 2. Further, a rear surface nozzle 8 is arrangedbelow the rotating table 3 to supply a liquid agent or pure water to therear surface of the to-be-cleaned substrate 2 such as a wafer placed onthe table from below. In this case, pure water includes ultra-purewater. Further, a heating device (heater) 11 for raising the temperatureof pure water and a control mechanism (controller) 12 for controllingthe operations of the respective constitutional parts are provided inthe substrate cleaning apparatus 1.

A method for cleaning the to-be-cleaned substrate such as a siliconwafer by use of the substrate cleaning apparatus 1 is explained withreference to FIG. 2.

First, a to-be-cleaned substrate 2 such as a silicon wafer is loaded onthe rotating table 3 in the substrate cleaning apparatus 1 while thepattern surface on which a wiring pattern is formed is set upward (step(a)).

Next, a mixture of sulfuric acid and hydrogen peroxide is supplied as anacid liquid agent from the acid liquid agent supply nozzle 4 to theto-be-cleaned substrate 2. That is, the mixture is applied to thepattern surface of the to-be-cleaned substrate 2 to clean the patternsurface. On the other hand, hot pure water of approximately 60 to 80° C.is applied from the nozzle 8 to the rear surface opposite to the patternsurface to wash out the acid liquid agent which comes round to the rearsurface of the substrate and raise the temperature of the substrate 2.At this time, the rotating table 3 is rotated at a low speed ofapproximately 15 to 30 rpm (step (b)).

The cleaning process for the substrate rear surface by use of hot purewater is not necessarily performed if an amount of supply of the acidliquid agent is relatively small and an amount of the acid liquid agentcoming round to the substrate rear surface is small.

Next, emission of the cleaning liquid is interrupted and the rotatingtable 3 is kept rotated at a low speed of approximately 15 to 30 rpm forapproximately 20 seconds. During this period of time, the acid liquidagent is uniformly spread over the substrate 2 to uniformly clean thesubstrate (step (c)).

The steps (a) to (c) are repeatedly effected twice or more, preferably,three times.

Next, a rinsing process is effected by use of hot pure water of 60 to80° C. while the rotating table 3 is kept rotated at a low speed ofapproximately 15 to 30 rpm. Hot pure water whose temperature is raisedby the pure water heating mechanism 11 is applied to the pattern surfaceof the to-be-cleaned substrate 2 from the pure water/alkaline liquidagent supply nozzle 5 to effect the rinsing process and a process forapplying hot pure water to the rear surface of the substrate from therear surface nozzle 8 is effected (step (d)).

After this, the cleaning cup 6 is moved upward, for example, and whileit is held in the upwardly moved position, hot pure water is emittedfrom a dedicated nozzle (not shown) or the pure water/alkaline liquidagent supply nozzle 5 to the inner wall of the cup 6 to clean the innerwall of the cleaning cup 6. The cleaning step is effected to clean theacid liquid agent which has been splashed and attached to the inner wallof the cleaning cup 6. At this time, while the rotating table 3 is keptrotated at a low speed of approximately 15 to 30 rpm, hot pure water isapplied to the rear surface opposite to the pattern surface (step (e)).

Next, while the rotating table 3 is kept rotated at a low speed ofapproximately 15 to 30 rpm, super sonic (megasonic) cleaning isperformed by use of an alkaline liquid agent (diluted NH₄OH solution).For example, an alkaline liquid agent subjected to the super soniccleaning of 1.5 MHz is emitted from a dedicated nozzle (not shown) orthe pure water/alkaline liquid agent supply nozzle 5 to theto-be-cleaned substrate 2 for approximately 3 minutes. The alkalineliquid agent contains an NH₄OH solution diluted by mid-temperature purewater lower than approximately 60° C. and is applied to the patternsurface of the to-be-cleaned substrate 2. At this time, hot pure waterof approximately 60 to 80° C. is applied to the rear surface of theto-be-cleaned substrate (step (f)).

Then, the cleaning process of the to-be-cleaned substrate 2 is effectedby use of an alkaline liquid agent or hot pure water. That is, a dilutedNH₄OH solution used as an alkaline liquid agent or hot pure water issupplied from the pure water/alkaline liquid agent supply nozzle 5 ontothe to-be-cleaned substrate 2 to clean the same. On the other hand, hotpure water of approximately 60 to 80° C. is applied to the rear surfaceopposite to the pattern surface. At this time, it is assumed that therotating table 3 is kept rotated at a low speed of approximately 15 to30 rpm (step (g)).

Next, a spin drying process for the to-be-cleaned substrate is effected.The drying process is effected by rotating the rotating table 3 at amid-speed (approximately 100 to 200 rpm) which is several times the lowspeed at first and then rotating the rotating table at a high speedhigher than approximately 700 rpm (step (h)).

The steps (f) to (h) are repeatedly effected twice or more, preferably,three times.

According to the first embodiment, by performing the cleaning process byuse of an alkaline liquid agent after the cleaning process by use of anacid liquid agent, a neutralization reaction between the acid and alkaliis caused so as to efficiently remove the acid liquid agent remaining onthe surface of the to-be-cleaned substrate. Further, by the cup cleaningprocess after washing-out of the acid liquid agent, the acid liquidagent attached to the cleaning chamber of the substrate cleaningapparatus can be washed out before the drying process and contaminationof the to-be-cleaned substrate due to fallout of salt formed on theinner wall of the cup can be prevented.

(Second Embodiment)

In the second embodiment, the step (b) (acid liquid agent supply step)and the step (c) (cleaning step by use of acid liquid agent) in thefirst embodiment are explained in detail.

FIGS. 3 and 4 are partial cross sectional views of a cleaning apparatushaving a to-be-cleaned substrate such as a silicon wafer loaded thereon,for illustrating a cleaning step by use of acid liquid agent in astepwise fashion. For easy understanding, portions which are the same asor similar to those of FIG. 1 are denoted by the same referencenumerals. This applies to the succeeding embodiments.

A rotating table 3 supporting the to-be-cleaned substrate 2 is rotatedby a rotating shaft 7. An acid liquid agent 13 is supplied from an acidliquid agent supply nozzle 4′ to the pattern surface of theto-be-cleaned substrate 2. In the above substrate cleaning apparatus, asmall amount of acid liquid agent 13 is emitted to the pattern surfaceof the to-be-cleaned substrate 2. At this time, the to-be-cleanedsubstrate 2 is rotated at a low speed of approximately 15 to 30 rpm.Further, the acid liquid agent supply nozzle 4′ is moved along theto-be-cleaned substrate 2 so as to cause the acid liquid agent 13 toeasily spread over the surface of the substrate (FIG. 3).

It is explained in FIG. 1 that the acid liquid agent supply nozzle 4 isfixed on the cleaning cup and the top end (emission port) thereof isarranged to be directed to the surface of the to-be-cleaned substrate,but the arrangement of the nozzle is not limited to this case. In thesecond embodiment, the acid liquid agent supply nozzle 4′ is mounted onan arm (not shown) and constructed to move along the surface of theto-be-cleaned substrate in the cleaning cup 6.

Next, the acid liquid agent supply nozzle 4′ is moved from the upperportion of the to-be-cleaned substrate 2 to the exterior. After this,the to-be-cleaned substrate 2 is rotated at a low speed of approximately15 to 30 rpm for approximately 20 seconds. As a result, it becomespossible to uniformly spread the acid liquid agent 13 on the surface ofthe to-be-cleaned substrate 2 and the cleaning process for the entiresurface of the substrate proceeds during this period of time (FIG. 4).

The above steps are repeatedly effected twice or more, preferably threetimes.

(Third Embodiment)

In the third embodiment, the step (e) (cup cleaning) in the firstembodiment is explained in detail. If splashed acid liquid agent is keptattached to the inner surface of the cup 6, salt is formed on the innersurface of the cup and causes dust in the later cleaning step by use ofan alkaline liquid agent and it is not preferable. In order to solve theabove problem, the cup cleaning step is effected to remove the acidliquid agent attached to the inner surface of the cup 6 after thecleaning step by use of the acid.

In FIG. 5, a rotating table 3 supporting the to-be-cleaned substrate 2is rotated by a rotating shaft 7. An acid liquid agent 13 is suppliedfrom an acid liquid agent supply nozzle 4 (not shown) to the patternsurface of the to-be-cleaned substrate 2.

In the third embodiment, pure water 15 is emitted from a cleaningchamber cleaning nozzle 14 while the acid liquid agent 13 is coated onthe to-be-cleaned substrate 2. During the cleaning time, the cleaningcup 6 constituting the cleaning chamber is moved upwardly by a movingmechanism 16 so that it can be easily cleaned. In FIG. 5, the originalposition of the cleaning cup 6 is indicated by broken lines and theupwardly moved position is indicated by a solid line. After cleaning,the cleaning cup 6 is moved downward and returned to the positionindicated by the broken lines.

In the third embodiment, if the pure water 15 emitted from the cleaningchamber cleaning nozzle 14 is set to a high temperature of approximately60 to 80° C., the cleaning effect is enhanced and a step of drying theinner wall of the cleaning cup 6 can be rapidly effected. In the thirdembodiment, since the cleaning chamber can be rapidly cleaned, the nextdrying step can be efficiently effected.

In the third embodiment, an example in which the dedicated nozzle 14 isused as a cup cleaning nozzle is explained, but this is not limitativeand it is possible to make the pure water/alkaline liquid agent supplynozzle 5 movable and use the same to clean the cleaning cup 6.

(Fourth Embodiment)

In the fourth embodiment, the step (g) (rinsing step by use of alkali orhot pure water) in the first embodiment is explained in detail.

In the fourth embodiment, hot pure water (80° C.) or diluted alkalineliquid agent 18 is emitted from a pure water/alkaline liquid agentsupply nozzle 5 mounted on the cleaning cup 6 after the cleaning step byuse of an acid liquid agent. If pure water is used, hot pure water 18whose temperature is raised by the pure water heating mechanism 11 ofFIG. 1 is applied to a portion slightly separated from the center of thesurface of the to-be-cleaned substrate 2. By applying the hot pure water18 as shown in FIG. 6, the temperature of the surface of the substrate 2becomes maximum in a position near the center and the cleaning effect isfurther enhanced.

As described in the first embodiment, if the drying step is effected byuse of the centrifugal force by the high-speed rotation of approximately700 rpm or more, pure water in the central portion tends to remain sincethe centrifugal force at the center of the surface of the to-be-cleanedsubstrate is minimum. If hot pure water of approximately 80° C. isemitted to the surface of the to-be-cleaned substrate before spindrying, the substrate temperature can be raised at the time of drying.At this time, the temperature of the surface of the to-be-cleanedsubstrate can be made maximum in a position near the center by applyingthe hot pure water to a position slightly separated from the center ofthe surface of the to-be-cleaned substrate. Thus, the drying processstarts from the center of the surface of the to-be-cleaned substrate.

(Fifth Embodiment)

In the fifth embodiment, the step (h) (spin drying step) in the firstembodiment is explained in detail.

In the fifth embodiment, a rinsing process by use of hot pure water ofapproximately 60 to 80° C. is effected after the megasonic cleaningprocess for the to-be-cleaned substrate by use of a diluted alkalineliquid agent. After interrupting emission of the hot pure water, theto-be-cleaned substrate 2 is rotated at a low speed lower than the highrotation speed of approximately 100 to 200 rpm and then theto-be-cleaned substrate is rotated at a high speed of approximately 700rpm or more after the drying process for the surface of theto-be-cleaned substrate 2 extends to a preset area (generally, to aportion such as the end portion of the substrate in which the pattern isnot formed).

Thus, if the rinsing process by use of the hot pure water ofapproximately 60 to 80° C. is effected, the drying process starts fromthe center of the surface of the to-be-cleaned substrate 2. Further, thedrying process is effected by rotating the substrate at a speed ofapproximately 100 to 200 rpm which is not so high until pure water 18remaining on the surface of the to-be-cleaned substrate 2 exists only onthe end portion of the substrate which lies outside the formed patternas shown in FIG. 7, and after this, the drying process is effected byrotating the substrate at a high speed of approximately 700 rpm or more.

In the fifth embodiment, since the temperature of the to-be-cleanedsubstrate is previously raised, the surface of the to-be-cleanedsubstrate can be dried by rotating the substrate at a speed(approximately 100 to 200 rpm) which is not so high and pure water willnot run at a high speed on the surface of the to-be-cleaned substrate.As a result, friction between the pure water and the substrate surfacebecomes small to suppress occurrence of static electricity. Even if thesubstrate is rotated at a high speed (approximately 700 rpm or more)after the drying process for the surface of the to-be-cleaned substratehas extended to a certain area, pure water will not run at a high speedon the surface of the to-be-cleaned substrate 2. The end portion of theto-be-cleaned substrate can be dried by thus rotating the substrate at ahigh speed.

(Sixth Embodiment)

In the sixth embodiment, internal pressure adjusting means of thecleaning nozzle is explained.

Like the substrate cleaning apparatus of FIG. 1, a substrate cleaningapparatus in the sixth embodiment includes a cleaning chamber forreceiving a to-be-cleaned substrate, a nozzle arranged in the cleaningchamber, for supplying an acid liquid agent, a hot pure water supplynozzle arranged in the cleaning chamber, and a pure water heatingmechanism arranged in the cleaning chamber and further includes a branchline 24 formed in intermediate portions of pipes 21, 22 extending fromthe pure water heating mechanism to the hot pure water supply nozzles 5,8, for lowering the water pressure in the pipes 21, 22.

The substrate cleaning apparatus has an open/close valve 25 provided inthe branch line 24 and is so constructed as to emit hot pure water ofapproximately 60 to 80° C. from the hot pure water supply nozzles 5, 8or interrupt emission of pure water and open the valve 25 to lower thepressure in the pipes 21, 22.

In the sixth embodiment, a filter 23 is provided between the pure waterheater (pure water heating mechanism) 11 (FIG. 1) and the pure watersupply nozzles 5, 8. The pipe 21 extending from the heater is coupled tothe inlet port of the filter 23 and the pipe 22 extending to the purewater supply nozzles 5, 8 is coupled to the outlet port of the filter23. Further, the branch line 24 is coupled to an air vent port of thefilter 23.

Leakage of liquid from the pure water supply nozzles 5, 8 at the time ofnon-emission time can be prevented by opening the air operate valve 25at the same time as interruption of emission of hot pure water to lowerthe pressure in the pipes 21, 22.

Thus, if the heating mechanism for pure water or liquid agent isprovided in the cleaning chamber of the substrate cleaning apparatus,the pressure in the pipe can be adequately changed by providing the valein the branch system of the branch line and opening/closing the valve.Particularly, when hot pure water is emitted before spin drying, thepressure in the pipe can be lowered by opening the vale provided in thebranch system at the same time as interruption of emission of pure waterand dropping of leaked liquid from the nozzle at the time of spin dryingcan be prevented.

As described above, in the above embodiments, a case wherein the waferof silicon, for example, is used is explained, but this invention is notlimited to the wafer and can also be applied to a liquid crystalsubstrate and photo-mask, for example.

Further, if an oxidizing agent supply nozzle and reducing agent supplynozzle are provided in the substrate cleaning apparatus with the sameconstruction as shown in FIG. 1, it becomes possible to attain asubstrate cleaning method for performing a process including a step ofoxidizing impurities on the surface of a to-be-cleaned substrate by useof an oxidizing agent at the initial stage and a step of cleaning theto-be-cleaned substrate by use of a reducing agent after completion ofthe oxidizing step so as to efficiently remove the oxidized impuritiesat the final stage.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A substrate cleaning apparatus comprising: a cleaning cup configuredto receive a to-be-cleaned substrate; a table disposed in the cleaningcup, configured to support the to-be-cleaned substrate; a first nozzledisposed in the cleaning cup, configured to supply an acid liquid agent;a second nozzle disposed in the cleaning cup, configured to supply analkaline liquid agent; a third nozzle disposed in the cleaning cup,configured to supply hot pure water; a pure water heating mechanismconfigured to supply the hot pure water; a branch line formed in anintermediate portion of a pipe extending from the pure water heatingmechanism to the third nozzle configured to supply the hot pure water tolower water pressure in the pipe; and a control mechanism configured tocontrol operations of the first to the third nozzle and the pure waterheating mechanism; and an open/close valve provided between the branchline and the pipe, wherein the control mechanism controls the open/closevalve to interrupt emission of hot water from the third nozzle byopening the open/close valve to lower the pressure in the pipe.
 2. Thesubstrate cleaning apparatus according to claim 1 wherein the pure waterheating mechanism controls the temperature of the hot pure water in arange of 60° C. to 80° C.
 3. The substrate cleaning apparatus accordingto claim 1, wherein the to-be-cleaned substrate Supporting table has anopening configured to substantially expose a rear surface of theto-be-cleaned substrate and is made rotatable.
 4. The substrate cleaningapparatus according to claim 3, wherein the third nozzle for supplyinghot pure water is disposed below the to-be-cleaned substrate supportingtable to emit hot pure water to the rear surface of the to-be-cleanedsubstrate.
 5. The substrate cleaning apparatus according to claim 1,further comprising a fourth nozzle configured to clean the cleaning cup.6. The substrate cleaning apparatus according to claim 1, furthercomprising a moving mechanism configured to change a relative positionbetween the cleaning cup and the to-be-cleaned substrate supportingtable.